1. Field of the Invention
The present invention relates to a method of controlling a heating cooking apparatus, such as a drawer-type microwave oven in which a drawer body on which a food to be heated is placed can be withdrawn from a cooking-apparatus main body.
2. Description of the Related Art
It is commonly known that microwave cooking is prone to overcooking without some smart cooking sensors.
Weight sensor was among the earliest cooking sensors for microwave cooking, which adjusts the cooking duration according to the food weight.
Although weight sensors were used to be the most popular, and are still pretty popular, among the microwave ovens with turntables, it is regarded impossible to implement a weight sensor in drawer type microwave ovens at a reasonable cost because the cooking chamber draws out and in from the microwave oven main body before and after the microwave cooking respectively; other sensing measures must be considered in the preserve of drawer-type microwave ovens.
Humidity cooking sensors detect the floating vapor coming from the foods being cooked, emitting timidly at first and fluently later on when water in the foods starts boiling actively.
Thus, by monitoring cooking chamber humidity continuously by a single humidity sensor, it is economically feasible to detect the state of cooking of various foods in various quantities by the humidity and its dependency during cooking process.
The present invention provides a brand-new and practical management system of humidity sensor to realize both smart cooking duration control and countermeasures against overcooking by implementing a few check points within the humidity sensing and cooking duration control program in drawer-type microwave ovens as calculated upon data from abundant cooking efforts in our laboratories.
FIG. 5 is a perspective view of a heating cooling apparatus of a conventional construction, and FIG. 6 is a side view of the heating cooking apparatus shown in FIG. 5. The heating cooking apparatus shown in FIGS. 5 and 6 is provided with a cooking-apparatus main body 1 having a heating chamber 3 for the heating cooking of an object to be heated and a drawer body 2 that can be pushed into and pulled out of the cooking-apparatus main body 1. The drawer body 2 has an opening and closing door 6 for opening and closing the heating chamber 3 and a heating receptacle 7 for housing an object to be heated by placing the object to be heated thereon. The drawer body 2 is disposed so as to be movable within the cooking-apparatus main body 1 in such a manner that the drawer body 2 can be withdrawn to the front side from within the heating chamber 3 of the cooking-apparatus main body 1. A moving mechanism 4 for moving the drawer body 2 within the cooking-apparatus main body 1 is constructed as a sliding mechanism using rails. The heating receptacle 7 has side walls on the right and left sides, a back wall on the back side that is disposed within the heating chamber 3 of the cooking-apparatus main body 1, and an opening that opens upward, and is provided with the opening and closing door 6 at the front. When the opening and closing door 6 closes the opening of the heating chamber 3, the inner space of the heating chamber 3 becomes an enclosed space formed by the inner wall surfaces of the cooking-apparatus main body 1 and the drawer body 2 and is configured to prevent microwaves, which are radiated to the interior of the heating chamber 3 to heat an object to be heated, from leaking.
The opening and closing door 6 of the drawer body 2 is supported on the cooking-apparatus main body 1 by the right and left side wall positioned outside the heating chamber 3 via the moving mechanism 4. The moving mechanism 4 is constituted by a fixed rail 9 and a moving rail 8 made of an angle, which slides along the fixed rail 9. The fixed rail 9 is attached to the right and left side walls of the heating chamber 3 of the cooking-apparatus main body 1 outside the heating chamber 3. The moving rail 8 is attached to the inner wall surface of the opening and closing door 6 via metal fittings so as to extend from the inner wall surface of the opening and closing door 6 of the drawer body 2 toward the interior of the heating chamber 3 of the cooking-apparatus main body 1. Because the moving mechanism 4 is provided outside the heating chamber 3, it is unnecessary to use expensive parts or materials having high heat resistance and flame resistance in fabricating the moving rail 8 and the fixed rail 9, and there is no fear that the moving rail 8 and the fixed rail 9 might be affected by microwaves radiated to the interior of the heating chamber 3, nor is there any fear of discharges by microwaves. A driving mechanism for driving the moving mechanism 4, though not shown in the figures, has a DC motor and a transmission mechanism coupled to a rotational output shaft of the DC motor, such as gears, and a pinion positioned in the last stage of the transmission mechanism has a meshing engagement with a rack attached to the moving rail 8. The drawer body 2 can be pushed into and pulled out of the cooking-apparatus main body 1 by rotating the pinion through the output of the DC motor.
Compared to general stationary microwave ovens, thanks to the characteristics of the drawer construction, many drawer-type heating cooking apparatus, such as microwave ovens, are constructed to have a flat shape with a wide bottom surface in the interior of the heating chamber 3 inside the heating-cooking apparatus, and with a small height. Therefore, a large amount of food can be placed within the heating chamber 3 because of the wide bottom surface area for the inside capacity, and it can be said that changes in the amount of the placed food are greater than in the stationary type.
In heating cooking apparatus such as microwave ovens, there has been publicly known an automatic cooking sequence that involves providing a humidity sensor that detects steam in the heating chamber 3, detecting that the generation of steam becomes active as the food temperature rises during the progress of heating cooking, and judging the progress status of heating cooking.
In automatic heating cooking apparatus using such a humidity sensor as described above, a detection point (a steam volume) is determined according to the manner in which steam is generated, which depends on the kinds of foods, and the heating time elapsing from the detection point until the finish of cooking is determined on the basis of the time that elapses from the start of heating to the detection point.
Also, it has been publicly known that an abnormal state, such as a case where heating processing is performed under no load, that is, without the presence of an object to be heated, is detected by using the functions of a humidity sensor. That is, this technique has a safety mechanism by which it is judged that an abnormal state, such as a no-load state, has occurred when a prescribed humidity is not detected by a given time after the start of heating cooking and long-time heating is avoided by forcedly finishing the heating when steam is not detected by a given time according to menus.
By inputting information on the weight of food using a weight sensor in automatic heating cooking using a humidity sensor, it is possible to adjust the heating time that elapses from a detection point to the finish of cooking according to changes in the amount of food. However, in a microwave oven not using a turn table, which is a rotary placement table, for structural reasons it is difficult to incorporate a weight sensor. Because of cost constrains, generally, a weight sensor is not built in microwave ovens of prevailing price whose functions are narrowed down to microwave heating.
Even when only a humidity sensor is used, by adjusting control conditions according to the kinds of foods, it is possible to perform substantially accurate automatic cooking for a given amount of food, but it is difficult to automatically adapt to variations in the amount of food. If conditions are set on the basis of a case where the amount of food is large, there is a possibility of overheating when the amount of food is small. Conversely, if conditions are set on the basis of a case where the amount of food is small, there is a possibility that heating becomes insufficient when the amount of food is large.
For the above-described structural reason, it can be said that drawer-type heating cooking apparatus have a wide weight range of placed food and that the weight range tends to vary. Furthermore, also the distance between the position where a food is placed and the humidity sensor is apt to vary and hence the detection accuracy of the humidity sensor tends to vary. Also, because drawer-type microwave ovens generally do not use a turn table, which is a rotary placement table, variations in the distance between the position where a food is placed and the humidity sensor are not averaged. Therefore, the distance from the humidity sensor is apt to vary according to the manner in which a food is placed within the heating chamber 3, and cooking results tend to vary in the case of automatic cooking using the humidity sensor.
It is possible to reduce variations in the results of automatic cooking by increasing the number of humidity sensors and detecting the humidity at a plurality of points of the heating chamber. However, because the number of humidity sensors to be installed increases in order to cope with all situations by various kinds of heating states of food, the manufacturing cost of heating cooking apparatus rises and problems such as complex control programs occur.
There has been proposed a method of preventing abnormal heating that involves measuring variations in the weight of an object to be heated during heating thereof by use of weight measuring means (a weight sensor), calculating an abnormal heating judgment weight by a calculation formula set beforehand by abnormal heating judgment weight calculating means on the basis of high frequency outputs and the time that elapses from the start of heating to the detection of steam by a humidity sensor, comparing this abnormal heating judgment weight with a weight loss of the object to be heated, and detecting an abnormally heated state from that fact that the weight loss has reached the abnormal heating judgment weight (Japanese Patent Laid-Open Publication No. 2003-214632).
Also, there has been proposed a method that involves providing an absolute temperature sensor that detects the temperature of exhaust air from a heating chamber as absolute temperature in the vicinity of an exhaust air port of a microwave oven, judging the heated state of an object to be heated within the heating chamber on the basis of detection outputs of this sensor, and detecting abnormal heating thereby (Japanese Patent Laid-Open Publication No. 62-126589).
Therefore, there are problems to be solved in an aspect that involves beforehand determining a heating time from the start of heating and a critical steam volume during this time on the basis of a steam curve that fixes a relationship between heating time and a generated steam volume, and detecting an abnormally heated state of the object to be heated, such as a no-load heating condition and a heated state which is such that a maximum volume is exceeded, on the basis of an actual heating time of an object to be heated and a generated steam volume.